South Tower passageway: Barbara (1997)
"The north and south towers are lower than the central one and are now in a greater state of ruin (pl 38c). The south tower contains a passageway with portions of the upper part intact. Presumably one entrance was in a plain inset panel of the first zone of the south side whence a stairway led upward to the level of the roof of the building. Five of the final upper risers are intact. From the top of the series of steps the passage extends horizontally westward 1.28 m., then northward 3.45 m. to the margins of the fallen masonry (pl. 40a); this portion is vaulted. The passageway had no doubt continued 70 cm. farther to open onto the roof of Room 1 (fig. 109). No indications of a passage were seen in either of the other towers."
(Ruppert & Denison 1943:87)